In the art of torque applying tools for tightening screw fasteners and the like, it is common practice to provide and use tools which are such that the torsional forces applied to fasteners worked upon is known, limited and/or controlled. Such tools or wrenches are commonly qualified as "torque wrenches".
In the art of torque wrenches, there is a special class of torque wrench commonly called "power torque wrenches". Power torque wrenches are pneumatically or hydraulically powered tools which characteristically include elongate rigid frames, power output shafts extending transverse of and rotatably carried by the frames at one end thereof, ratchet drive means carried by the shafts to establish rotary driving engagement therewith when turned in one direction and which have lever arms projecting radially outwardly therefrom; and pneumatic or hydraulic cylinder and ram units connected with and between the ends of the lever arms of the ratchet means and the other ends of the frames. The output shafts of such power torque wrenches carry work or fastener engaging tools, such as fastener head engaging sockets, at one of their ends. Such sockets or fastener engaging tools, while commonly separable from their related shafts, are, when engaged therewith, considered a part of their related shafts or wrench structures.
The mechanical geometry of power torque wrenches of the character described above is substantially fixed and the power rating of the cylinder and ram units thereof is substantially fixed. Accordingly, the power output or torsional forces delivered by the output shafts of such wrenches is substantially directly proportional to the pressure on the motive fluid medium delivered to the cylinder and ram units. By delivering motive fluid to the cylinder and ram units of such wrenches at selected pressures, the torsional forces delivered by the wrench structures onto related fasteners or the like is predetermined and known.
In using such wrenches, their output shafts, with related fastener engaging tools or sockets coupled therewith, are arranged in axial alignment with headed fasteners to be worked upon, with the tools or sockets engaged with the heads of the fasteners. The frames of the wrenches are then suitably stopped to prevent their rotation about the axes of the fasteners and to assure that necessary reaction through and between the wrench structures and the fasteners is attained. Thereafter, motive fluid is intermittently delivered to and exhausted from the cylinder and ram units to effect reciprocating operation thereof, oscillating rotary driving of the ratchet means and resulting intermittent rotary driving of the assembled and engaged shafts sockets and fastners.
For effective use and operation of power torque wrenches of the character referred to above, it is highly important that axial alignment of the output shaft and the fasteners worked upon be established and maintained. Any substantial misalignment of the shafts, sockets and/or fasteners resulting in any notable relative movement and/or binding therebetween materially alters the torque delivered by the output shafts to the fasteners and renders the wrenches incapable of applying known predetermined forces onto and through the fasteners. Further, if the shafts, sockets and fasteners are sufficiently misaligned to cause binding and relative working between the related parts, the exerting of high forces therebetween often results in extensive and irreparable damage to the noted related parts.
In practice, stopping the frames of power torque wrenches against rotation relative to the fasteners worked upon and to thereby attain necessary reaction in and through the wrench structures and fasteners often presents special problems. When the fasteners worked upon are close to strong and structurally sound supporting structures against which the wrench frames can be stopped, little difficulty exists in effectively stopping the frames. However, where no available or suitable stopping or reacting structures are available to engage and stop the wrench frames, special and oftentimes costly and difficult to use stop and/or anchoring means and structure must be devised and used to stop the wrench frames.
It has been determined that in the great majority of situations where power torque wrenches are used, there exists a plurality of spaced apart headed screw fasteners which must be worked upon or tightened and that by providing and using suitable anchoring mechanisms attached to the torque wrench structures and engageable with selected fastener heads in a series or group of related fasteners, can effectively serve to anchor and stop the frames of the wrenches, as desired. One such anchoring mechanism provided by the prior art comprises an elongate link having one end pivotably connected with the free end of its related power torque wrench frame, remote from the drive shaft of the wrench, and having a fastener head engaging socket fixed to its other end. With this anchoring attachment related to and made a part of a power torque wrench structure, the wrench structure is related to and engaged with a first screw fastener to be tightened in a regular manner such as described above and the wrench frame and the like of the anchoring mechanism are pivoted to align the socket on the link with the head of another or second available fastener head and the socket is moved into engagement with that head; thereby effectively anchoring and stopping the frame, preparatory to operating the wrench and tightening the first fastener.
While the above noted type of anchoring mechanism or attachment for power torque wrenches has proven to be effective in a notable number of frequently encountered situations, it has proven to be so undependable in a sufficient number of instances to cast serious doubts regarding its general utility. The principal shortcoming found to exist in the use of the above noted form of anchoring mechanism resides in the fact that when wrenches with such anchoring mechanisms related to them are engaged with and between first and second fastener heads, as noted above, and the fastener heads are on spaced apart planes, necessary alignment of the fasteners with their related parts of the wrench structures and anchoring mechanisms cannot be attained. That misalignment of parts which oftentimes exists is sufficient to cause a binding of parts which prevents the wrenches from operating properly, and results in damage to the fasteners and to the parts and/or portions of the wrench structures related thereto.
In accordance with the above, a prerequisite to the effective and safe use of the above noted form of anchoring mechanisms for power torque wrenches is that the pairs of fastener heads with which the wrenches and anchoring mechanisms are related be on a common plane or be so close to a common plane that misalignment of the several related parts cannot or is not likely to occur.
It has been determined that when a power torque wrench with an anchoring mechanism of the character referred to above is engaged with and between a pair of related fastener heads entered into a common surface of a related structure, one of the fasteners is fully engaged in that structure and the other fastener is just entered into that structure, the heads of the fasteners most often occur on different planes which are spaced apart a sufficient distance to prevent necessary alignment of parts and safe operation of the wrench structure.